Lithium-strontium soap greases from oxidized petroleum fractions



the waxate soap.

United States Patent LITHIUM-STRONTIUM SOAPGREASES FROM OXIDIZEDPETROLEUM FRACTIONS George W. Eckert, Glenllam, N. Y., assignor to TheTexas Company, New, York, N. Y., a corporation of Delaware No Drawing.Application December-24, 1952, Serial No. 327,933:

3 Claims. ct. 252-40 This invention relates to improvedlubricatinggrease compositions and more particularly to lubricating greasescontaining mixed lithium and strontium soaps of oxidized petroleumfractions.

It is Well known in the art to employ oxidized petroleum fractions asthe saponifiable material in grease making, and greases have beenprepared-from such materials employing various metals as the metalcomponent of However, these oxidates are considerably different in manyrespects from the natural fats and fatty acids in their grease makingproperties, and difficulties have been encountered in producing greasesof the desired properties. from these materials. The chief difficulty,which has beenvfound ina greater or less extent with all greases of thistypeof the prior .art, is the tendency. of these greases to harden, orset up, in storage. This hardening is very objectionable from thestandpoint of marketability, and also seriously impairs the servicecharacteristics of the'greases for many purposes.

In accordance with this invention, very superior lubricating greases,having both excellent lubricating prop-j erties and storagecharacteristics, are obtained by employing as the essential thickeningagent a mixed lithium-strontium soapof a-saponifiable materialresultingfrom the oxidation of a petroleum fraction, the mixed lithium-strontiumsoap comprisingsubstantial proportions of each metal soap. The soap maysuitably. comprise lithium and strontium oxidatesoaps in, aproportion,of about 1 to 4 to about ,4 to 1 by weighuandpreferably in a proportionof aboutl to 1 to about 4 to l by weight. This mixed base soap isemployed in a suitable oleaginous vehicle in varying amounts to producegreases for various purposes ranging from semi-fluid to very stiff.Ordinarily, the soap content of the grease will be from about to about45 per cent by Weight.

The oxidates employed in preparing the greases of this invention areoxidized petroleum fractions containing considerable proportions ofsaponifiable materials, or separated saponifiable fractions of suchoxidized;

petroleum fractions such as have been employed hereto fore in greasemaking. They are obtained by oxidizing a petroleum fraction such as alubricating oil fraction,

crude or refined wax, slack Wax, or petrolatum attelevated:

The mixed lithium-strontium soaps are prepared from.

the petroleum oxidates by any of the conventional methods employed forobtaining mixed base, soaps, such as by coprecipitation or by mixingseparately prepared lithium and strontium soaps. They are mostconveniently prepared by the coprecipitation method, that is, by

saponification of the oxidate with lithium and strontium. hydroxides orother suitable compounds to' producedirectly a mixed soap of the desiredratio of lithium grease.

andstrontium soaps. An excess of lithium or strontium hydroxide, or ofboth lithium and strontium hydroxides, beyond the amounts required toreact with all of the saponifiable matter is employed in thesaponification, Preferably, an excess of lithium or strontium hydroxideis added suificient to give a free alkalinity ofabout 0.01 per cent toabout 10 per cent-by weight; of the finished In addition to thesespecial soaps, the greases of this invention may contain any of theusual additives such as, for example, oxidation and'corrosioninhibitors,extreme pressure agents, oiliness agents andso forth, as well as smallamounts of additional thickening agents such as polymeric materials andsolid lubricants such as carbon black. These greases. may also be mixed;or blended with greases of other types if desired toproduce greases ofspecial properties.

The oleaginous vehicle employed in the grease may be any suitable oil oflubricatingcharacteristics, which may be of mineral, vegetable, animalor synthetic origin, such as have been employed heretoforein,lubricating greases. Suitable mineral oils include both distillate andresidualfractions from parafiinic, napth enic or mixed base crude,ranging frorn fairly low to fairly. high ViSr cosities, such as fromabout 50 to about 1500 seconds Saybolt Universal viscosity at F. Theseoils may be obtained by, any of theusual refining methodssuch as acidtreating, solvent extraction, andso forth. For certain purposes, such asfor example the production of lowtemperature greases, various syntheticoils may be employed with particular advantage. As examples of suitableoils of this type may be mentioned high molecular weight aliphaticethers, such as normal hexyl ether, the alkyl esters of benzoic andphthalic acids, and the aliphatic dicarboxylic acid di-esters, such asdi;2-ethyl hexyl sebacate, di (secondary amyl) sebacate, di-Z-ethylhexyl azelate, di-isooctyl adipate, etc.

Thegrease preparation is suitably carriedout by charging a quantityofoxidate together with lithium and strontiumhydroxides in proportionateamounts to a-con ventional grease making kettle, where the mixture ismaintained at elevated 1 temperature below about 220 'F; with stirring,air blowing or other mechanical agitation untii the saponification'iscomplete. The temperature is thenincreasedto about 270 F. or higher andmain? tained at this increased temperature-for 'a time-sufii'cient toaccomplish dehydration. The-lubricating oilincluded in the grease ispreferably added to the initial charge also, or only a small amount ofthe oil may be added to the. initial charge andladditional' oil addedduring the saponification or after the dehydration to obtain a grease ofthe desired consistency. Other. saponifiable materials such as thenatural fats and oils commonly employed in grease making may also-beaddedwhere it isdesiredto obtain a mixed grease.

Greases preparedfrom mixed lithium-strontiumoxidate soaps as describedabove have-been found; to ,havevery different storage characteristicsfrom, the other. petroleum oxidate greases of the prior art, inadditiorrto, generally excellent lubricating characteristics.equivaientfto those obtainable with the very, expensivehighly-refiuednatural fats and fatty acids, It is particularlysurprising that oxidate greases of excellent lubricating characteristicsare obtained employing this combination of: metals, since attempts toproduce greases employing both 'litghium oxidate soaps and strontiumoxidate soaps separately have given veryainpromising results, thegreases produced being gel-like and unsatisfactory in texture andsoftening to an objectionable degree upon working, For example, a greasecomprising 20 per cent'of-lithiumoxid e; soap in a .naphtl1ene. baselubricatin il hay n 174 and a worked penetration of 274. A greasecomprising 20 per cent of strontium oxidate soap in a lubricating oil ofthe same type had an original unworked penetration of 217 and a workedpenetration of 312, and in addition it had a very low dropping point ofonly 222 F. However, greases prepared according to this invention byemploying both lithium and strontium oxidate soaps in combination havebeen characterized by excellent texture, and have tended to hardenslightly rather than to soften upon working. In addition, these greasesvery unexpectedly showed no hardening upon storage even for long periodsof time.

The following example is given as illustrative of the greases of thisinvention.

EXAMPLE A lubricating grease was prepared from the following materials:

Grams Wax oxidate 3,304 Mineral lubricating oil 5,600 LiOH (10%)(aqueous solution) 8,000 S1(OH)2.8H2O 900 The wax oxidate employed had aneutralization number of 250, a saponification number of 390 andcontained 14.0 per cent of unsaponifiables. It was obtained by oxidizinga paratfin wax obtained from a pressed distillate of SAE 10 grade. Theoxidation was carried out at a temperature of 270 F., a pressure of p.s. i. g. and an air rate of 20 cubic feet per hour per pound of charge.

The mineral lubricating oil was a refined naphthenc base distillate oilhaving a Saybolt Universal viscosity at 100 F. of about 300 seconds.

The grease preparation was carried out by charging the above materialsin the amounts given above to a steamheated grease kettle and heatingfor two hours at 200 F., with continuous stirring, until thesaponification was substantially complete. The temperature was thenincreased to 300 F., and the mass held at this temperature for two hoursto dehydrate, after which the temperature was allowed to fall and thegrease finally drawn at 216 F. A smooth, buttery grease was obtained.The following table shows the storage characteristics of this grease(Grease No. 7 of the table) as compared with those of greases preparedfrom the same mineral oil and oxidates of the same type, but containingditferent metals in place of lithium-strontium combination.

The above table shows the striking difference in storage characteristicsbetween the lithium-strontium oxidate grease and those of the othermetal oxidate greases representative of the oxidate greases of the priorart. As shown by the table, the lithium-strontium grease showedsubstantially no change in penetration on either the worked or theunworked basis during a six months storage test. On the other hand, allof the other oxidate greases hardened continuously during storage on thebasis of their unworked penetrations, with very large decreases inpenetration occurring after only two days of storage. Thelithium-strontium grease was also very resistant to change upon working,as shown by the small spread between the values found for the unworkedand the worked penetrations during the test, and the change whichoccurred was a slight hardening instead of the softening which is ageneral characteristic of other oxidate greases in this test.

in addition to its excellent storage properties as discussed above, thelithium-strontium oxidate grease of the example had all of thelubricating properties required of a very superior ball and rollerbearing grease, as shown by the standard tests, including a droppingpoint of 407 F., a high mean Hertz load, without E. P. additives of 31,excellent water resistance, as shown by a loss of only 4 per cent in thedynamic water resistance test, and satisfactory rust resistance for anuninhibited grease. In addition, the Navy gear wear test (MIL-G-3278) onthis grease was as follows: 0.4 gram Weight loss, brass on steel, 5pounds load, 1000 cycles; and 2.2 grams weight loss, brass on steel, 10pounds load, 1000 cycles. These values are equivalent to thoseobtainable with good grade com mercial ball and roller bearing greases.Very good results were also obtained with this grease in the torquebreakdown machine test with a Federal ball bearing at 250 F., runcontinuously for 168 hours. The machine was shut down for observation atthe end of this time with no failure. No grease leakage had occurred andthe hearing condition was satisfactory.

Obviously, many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof and, therefore, only such limitations should beimposed as are indicated in the appended claims.

I claim:

1. A lubricating grease comprising essentially an oleaginous vehicle asthe chief constituent thickened to a grease consistency with a mixedlithium-strontium soap Mineral oil, percent Penetration, ASTM, 77 F.:

Unworked basis:

Original grease. After 2 days After days After 6 months Worked basis:Original grease 298 331 316 24a After 2 days 201 310 291 263 After 14days.

After 30 days.

After 90 day After 6 month 1 Sample containing 0.5% of PSF-M, acommercial amine-type oxidation inhibitor.

of a saponifiable material obtained by the oxidation of a petroleum waxhaving a saponification number in the range from about 175 to about 450,said mixed lithiumstrontium soap consisting of lithium and strontiumsoaps in a proportion by weight from about 1 to 4 to about 4 to 1, andcontaining free alkalinity in an amount equal to about 0.01 to about 10per cent by weight of the grease,

2. Claim 1 wherein the soap consists of lithium and strontium soaps inabout a 3 to 2 proportion by Weight.

3. A lubricating grease comprising essentially a naphthene basedistillate lubricating oil having a Saybolt Universal viscosity of about100-400 seconds at 100 F. as the chief constituent, thickened with about25-45 per cent by weight of a mixed lithium-strontium soap of asaponifiable material having a saponification number in the ReferencesCited in the file of this patent UNITED STATES PATENTS 2,409,950 MeyerOct. 22, 1946 2,417,428 MeLennan Mar. 18, 1947 2,417,429 McLennan Mar.18, 1947 2,669,543 Hirsch Feb. 16, 1954

1. A LUBRICATING GREASE COMPRISING ESSENTIALLY AN OLEAGINOUS VEHICLE ASTHE CHIEF CONSTITUENT THICKENED TO A GREASE CONSISTENCY WITH A MIXEDLITHIUM-STRONTIUM SOAP OF A SAPONIFIABLE MATERIAL OBTAINED BY THEOXIDATION OF A PETROLEUM WAX HAVING A SAPONIFICATION NUMBER IN THE RANGEFROM ABOUT 175 TO ABOUT 450, SAID MIXED LITHIUMSTRONTIUM SOAP CONSISTINGOF LITHIUM AND STRONTIUM SOAPS IN A PROPORTION BY WEIGHT FROM ABOUT 1 TO4 TO ABOUT 4 TO 1, AND CONTAINING FREE ALKALINITY IN AN AMOUNT EQUAL TOABOUT 0.01 TO ABOUT 10 PER CENT BY WEIGHT OF THE GREASE.